Use Case Analysis

1. Use Case Analysis Chapter 6

2. Key Ideas • Use cases are a text-based method of describing and documenting complex processes • Use cases add detail to the requirements outlined in the requirement definition • Systems analysts work with users to develop use cases • Systems analysts develop process and data models later based on the use cases

3. Use Cases

4. Roles of Use Cases • A use case is a set of activities that produce some output result • Describes how the system reacts to an event that triggers the system • Trigger -- event that causes the use case to be executed • Event-driven modeling – everything in the system is a response to some triggering event

5. Modeling Use Cases • Complete piece of functionality • Main flow/Main success scenario • Subflows • Exensions/Alternate flows

6. Role of Use Cases • All possible responses to the event are documented • Use cases are helpful when the situation is complicated

7. Sample Format for a Written Use Case • Title – descriptive name, matches name in use case diagram • Primary actor – usually a user role • Stakeholders – any group or individual with an interest in the function of the use case • Precondition – conditions that must be satisfied in order to execute the use case

8. Sample Format for a Written Use Case - 2 • Minimal guarantee/Postcondition – outputs that can be expected if the service attempt failed • Success guarantee/Postcondition – outputs that can be expected if the service succeeds • Trigger – an event or action that initiates the use case • Main success scenario – description of sequence of interactions between actor and use case during the use case execution • Extensions – detailed description of how errors are dealt with

9. A sample written use case

10. Building Use Cases

11. Step 1: Identify the major use cases

12. Sample List of Events-Actions Based on Requirements Definition

13. Step 2: Identify the major steps within each use case

14. Step 3:Identify elements within steps

15. Step 4:Confirm the use case

16. Interim Summary • Use cases contain all the information needed for process modeling, but are easier for users to comprehend • Use cases are created in an iterative cycle of steps until they are considered accurate and complete

17. Exercise: Use Cases Describe one major use case from your team project (try to find the most important one) using the template provided (based on Fig. 6-4 on pg. 174).

18. The Four Basic UML Diagrams

19. USE CASE DIAGRAM

20. Use Case Diagram Concepts • Summarizes all use cases (for the part of the system being modeled) together in one picture • Typically drawn early in the SDLC • Shows the associations between actors and use cases

21. Use Case Diagram for Appointment System

22. Syntax for Use Case Diagram

23. Use Case Diagram for Specialized Actor

24. Extends and Includes Associations

25. Steps in Creating the Use Case Diagram 1. Identify Use Cases 2. Draw the system boundary 3. Place Use Cases on the diagram Group Use Cases into packages Add special Use Case associations 4. Identify the actors 5. Add associations

26. Exercise: Use Cases in UML Choose at least 5 functional requirements for your team project. Draw a use case diagram similar to Fig. 6-9 on P. 181 that represents these requirements as use cases, along with the appropriate actors.